Fluoroalcohol is known to be readily synthesized by treating an epoxy compound with HF, HF/pyridine, KHF2, or a similar agent (Non-Patent Documents 1 and 2). However, in the case where an optically active fluoroalcohol in which a fluorine atom is bound to an asymmetric carbon atom is produced, selective production of a desired optical isomer is difficult through employment of the above method, and the product is an isomer mixture. A desired optical isomer of interest can be separated from the mixture through an intricate purification operation such as optical resolution. Thus, a high-optical-purity final product is difficult to obtain at high yield.
A fluorine atom can be introduced to a specific site of an organic compound through a known method employing a fluorinating agent. Such a fluorinating agent is categorized into two types. One is an electrophilic fluorinating agent formally generating a fluorine cation, and the other is a nucleophilic fluorinating agent generating a fluoride anion. A variety of compounds such as HF are known to be nucleophilic fluorinating agents. Particularly when a compound such as diethylaminosulfur trifluoride (DAST) or 2,2-difluoro-1,3-dimethylimidazolidine (DFI) is reacted with an alcohol, an oxygen atom is known to be readily nucleophilic-substituted by a fluorine atom under mild conditions (Non-Patent Documents 3, 4, and 5).
One conceivable approach for synthesizing an optically active fluoroalcohol is treating an optically active diol serving as a source with the aforementioned fluorinating agent. However, when this approach is employed, selective fluorination of only one hydroxyl group of the diol is difficult to attain, and non-target compounds such as a difluoro compound in which two hydroxyl groups are completely fluorinated are readily formed. Thus, in this context, the approach is not suitable (Non-Patent Document 6 and Patent Document 1).
In order to produce an optically active fluoroalcohol through selective fluorination of a diol, reaction of only one hydroxyl group must be promoted. However, at present, difficulty is often encountered for selective introduction of a protective group. Thus, hitherto, there has never been known a technique for introducing a protective group into one hydroxyl group of a diol and selectively fluorinating the other hydroxyl group thereof, and an optically active fluoroalcohol has been considerably difficult to produce at high optical purity and yield.    Non-Patent Document 1:            Tetrahedron Letters, vol. 31, No. 49, 1990, pp 7209-7212            Non-Patent Document 2:            Journal of Fluorine Chemistry, vol. 16, 1980, pp 540-541            Non-Patent Document 3:            Journal of Organic Chemistry, vol. 40, No. 5, 1975, pp 574-578            Non-Patent Document 4:            Fine Chemical, vol. 31, No. 10 (2002) pp 5-12            Non-Patent Document 5:            Chemistry & Chemical Industry, vol. 55, No. 3 (2002), pp 259-262            Non-Patent Document 6:            Journal of the Chemical Society Perkin Transactions 2, 4, 1995, pp 861-866            Patent Document 1: JP11-181022A